Microelectronic substrate inspection equipment using helium ion microscopy

ABSTRACT

Microelectronic substrate inspection equipment includes a gas container which contains helium gas, a helium ion generator which is disposed in the gas container and converts the helium gas into helium ions and a wafer stage which is disposed under the gas container and on which a substrate to be inspected is placed. The equipment further includes a secondary electron detector which is disposed above the wafer stage and detects electrons generated from the substrate, a compressor which receives first gaseous nitrogen from a continuous nitrogen supply device and compresses the received first gaseous nitrogen into liquid nitrogen, a liquid nitrogen dewar which is connected to the compressor and stores the liquid nitrogen, and a cooling device that is coupled to the helium ion generator. The cooling device is disposed on the gas container, and cools the helium ion generator by vaporizing the liquid nitrogen. Related methods are also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2012-0003497 filed on Jan. 11, 2012 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

1. Field of the Invention

The present inventive concepts relate to microelectronic substrateinspection equipment and microelectronic substrate inspection methodsusing the same.

2. Description of the Related Art

With the increasing precision of semiconductor processes, pattern sizesare becoming smaller, and step heights are becoming greater. To inspecta pattern to see if the pattern has been formed according to designvalues, optical inspection equipment is generally used. However, opticalinspection equipment may have limitations in its detection capabilitydue to optical diffraction. Since the process of detecting a finepattern with a great step height requires an increasingly higher levelof precision, inspection methods for detecting fine patterns are beingresearched.

To overcome the limitations of the optical inspection equipment, anobject lens with a high numerical aperture (NA), light in ashort-wavelength range (e.g., deep ultraviolet (DUV),extreme-ultraviolet (EUV)), or various light irradiation methods arebeing used. However, there may be limitations in increasing thenumerical aperture by 1 or more or reducing the wavelength of a lightsource. To overcome the limitations of optical inspection equipment,electron beam inspection equipment, which images secondary electronsgenerated by irradiating electrons with high accelerated energy, hasbeen introduced. Electron beam inspection technology has developed to apoint where it can detect defects of about 10 nm and can provide aspatial resolution of several nanometers. However, an electron beam usedby the electron beam inspection equipment can cause electric charges tobe charged on a sample or cause damage and contamination of the sample.In addition, electron beam inspection equipment may require ahigh-vacuum or ultra-high vacuum operating environment and may onlyobtain 2D planar information, instead of stereoscopic information, dueto its small depth of focus (DOF).

SUMMARY

Aspects of the present inventive concepts can provide inspectionequipment which can obtain 3D stereoscopic information about a patternformed on a microelectronic substrate using a helium ion microscope(HIM).

Aspects of the present inventive concepts also can provide inspectionmethods which are employed to measure a step height of a pattern on amicroelectronic substrate using the microelectronic substrate inspectionequipment.

However, aspects of the present inventive concepts are not restricted tothe one set forth herein. The above and other aspects of the presentinventive concepts will become more apparent to one of ordinary skill inthe art to which the present inventive concepts pertain by referencingthe detailed description of the present inventive concepts given below.

According to some aspects of the present inventive concepts, there isprovided microelectronic substrate inspection equipment. Themicroelectronic substrate inspection equipment includes a helium gascontainer which contains helium gas, a helium ion generator which may bedisposed in the gas container and is configured to convert the heliumgas into helium ions and a wafer stage which may be disposed under thegas container in a path of the helium ions and on which a substrate tobe inspected is placed. The microelectronic substrate inspectionequipment also includes a secondary electron detector which is disposedadjacent and, in some embodiments above, the wafer stage, and isconfigured to detect electrons generated from the substrate, and acompressor which is configured to receive first gaseous nitrogen from acontinuous nitrogen supply device and to compress the received firstgaseous nitrogen into liquid nitrogen. The microelectronic substrateinspection equipment also includes a liquid nitrogen dewar which isconnected to the compressor and is configured to store the liquidnitrogen, and a cooling device which is configured to cool, for exampleto continuously cool, the helium ion generator by vaporizing the liquidnitrogen received from the liquid nitrogen dewar into second gaseousnitrogen, which may be disposed on the helium gas container, and iscoupled to the helium ion generator.

According to other aspects of the present inventive concepts, there isprovided a microelectronic substrate inspection method, the methodcomprising, providing a microelectronic substrate having a pattern,irradiating helium ions onto the substrate, and measuring a step heightof the pattern on the substrate by detecting particles generated fromthe substrate in response to the helium ions that are irradiated.

According to still other aspects of the present inventive concepts,there is provided a microelectronic substrate inspection method thatcomprises measuring a step height of a pattern on a microelectronicsubstrate using a helium ion microscope. Measuring may take place bymeasuring a slope width of the pattern at two different tilt angles ofthe substrate relative to the helium ion microscope. One of the twodifferent tilt angles may be about zero degrees. Moreover, the heliumion microscope may be operated continuously during the measuring theslope of the pattern at the two different tilt angles.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and features of the present inventiveconcepts will become more apparent by describing in detail exemplaryembodiments thereof with reference to the attached drawings, in which:

FIG. 1 is a schematic diagram of semiconductor substrate inspectionequipment according to embodiments of the present inventive concepts;

FIG. 2 is a schematic plan view of the semiconductor substrateinspection equipment shown in FIG. 1;

FIG. 3 is a schematic diagram of a helium ion microscope (HIM) used insemiconductor substrate inspection equipment according to embodiments ofthe present inventive concepts;

FIG. 4 shows a region B of FIG. 3;

FIG. 5 shows a region C of FIG. 3;

FIG. 6 is a diagram of an HIM used in semiconductor substrate inspectionequipment according to other embodiments of the present inventiveconcepts;

FIGS. 7 and 8 are diagrams of detectors used in semiconductor substrateinspection equipment according to other embodiments of the presentinventive concepts;

FIGS. 9A through 10B are diagrams illustrating a calculation of acontroller used in semiconductor substrate inspection equipmentaccording to other embodiments of the present inventive concepts; and

FIGS. 11 and 12 are flowcharts of operations that may be performed tomeasure step height according to various embodiments of the presentinventive concepts.

DETAILED DESCRIPTION OF EMBODIMENTS

The present inventive concepts will now be described more fullyhereinafter with reference to the accompanying drawings, in whichpreferred embodiments of the invention are shown. This invention may,however, be embodied in different forms and should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the invention to those skilled in theart. The same reference numbers indicate the same components throughoutthe specification. In the attached figures, the thickness of layers andregions is exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “connected to,” or “coupled to” another element or layer, it canbe directly connected to or coupled to another element or layer orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly connected to” or “directlycoupled to” another element or layer, there are no intervening elementsor layers present. Like numbers refer to like elements throughout. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. Thus, for example, a first element, afirst component or a first section discussed below could be termed asecond element, a second component or a second section without departingfrom the teachings of the present inventive concepts.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. It is noted that the use of anyand all examples, or exemplary terms provided herein is intended merelyto better illuminate the invention and is not a limitation on the scopeof the invention unless otherwise specified. Further, unless definedotherwise, all terms defined in generally used dictionaries may not beoverly interpreted.

Various embodiments will now be described relative to inspectionequipment for semiconductor substrates. However, it will be understoodthat various embodiments described herein may be used with anymicroelectronic substrate, such as a glass or other carrier substratethat includes dense microelectronic patterns. Hereinafter, semiconductorsubstrate inspection equipment according to some embodiments of thepresent inventive concepts will be described with reference to FIGS. 1through 5.

FIG. 1 is a schematic diagram of semiconductor substrate inspectionequipment according to some embodiments of the present inventiveconcepts. FIG. 2 is a schematic plan view of the semiconductor substrateinspection equipment shown in FIG. 1. FIG. 3 is a schematic diagram of ahelium ion microscope (HIM) used in semiconductor substrate inspectionequipment according to embodiments of the present inventive concepts.FIG. 4 shows a region B of FIG. 3. FIG. 5 shows a region C of FIG. 3.

Referring to FIGS. 1 and 2, the semiconductor substrate inspectionequipment according to some embodiments of the present inventiveconcepts includes a load port 1000, a front-end module 2000, a load lockchamber 3000, a main chamber 4000, and a controller 40. The load port1000 and the front-end module 2000 may be connected by a gate (notshown) through which semiconductor substrates can be moved. A surface ofthe front-end module 2000 which is not connected to the load port 1000is connected to the load lock chamber 3000. The front-end module 2000and the load lock chamber 3000 are connected to each other by a firstgate valve 3000 a. The load lock chamber 3000 and the main chamber 4000may be connected to each other by a second gate valve 3000 b. The firstgate valve 3000 a and the second gate valve 3000 b may be provided tocontrol the pressure between the front-end module 2000 and the load lockchamber 3000 and the pressure between the main chamber 4000 and the loadlock chamber 3000, respectively. If there is no difference in pressurebetween the main chamber 4000 and the front-end module 2000, the firstand second gate valves 3000 a and 3000 b and the load lock chamber 3000can be omitted. The semiconductor substrate inspection equipment may begreatly affected by vibrations. Thus, the load lock chamber 3000 and themain chamber 4000 are supported by an anti-vibration system 4020 thatcan absorb shock. The controller 40 may be electrically connected to themain chamber 4000. In the drawings, the controller 40 is connected to adetector 30 included in the main chamber 4000. However, the presentinventive concepts are not limited thereto.

Specifically, referring to FIGS. 1 and 2, the load port 1000 is a placeto which substrates to be inspected are fed and includes a plurality oftables 1010 on which the substrates can be placed. A substrate to beinspected may be contained in a cassette and then fed to the load port1000. However, the present inventive concepts are not limited thereto.

The front-end module 2000 is a place where a substrate to be inspectedis moved and may be maintained at atmospheric pressure. The front-endmodule 2000 includes a first robot arm 2020 and a filter 2010. The firstrobot arm 2020 may transfer a substrate placed on a table 1010 of theload port 1000 to a first holder 3020 of the load lock chamber 3000.Since the first robot arm 2020 can transfer substrates to be inspectedfrom a plurality of tables 1010 to the load lock chamber 3000, it maymove in a second direction y. The filter 2010 causes air to flow from anupper part of the front-end module 2000 to a lower part. If particles(such as dust) adhere to a substrate to be inspected, they may causeerrors in the inspection of the substrate. Therefore, the filter 2010may always move air downward.

The load lock chamber 3000 may include the first holder 3020 and asecond robot arm 3010. The first holder 3020 and the second robot arm3010 may be located in separate places in the load lock chamber 3000,and the separate places may be connected by a third gate valve 3000 c.The first holder 3020 is where a substrate transferred by the firstrobot arm 2020 is placed. The second robot arm 3010 may transfer asubstrate placed on the first holder 3020 to a second holder 20 (alsoreferred to as a “wafer stage 20”) in the main chamber 4000. The loadlock chamber 3000 may be connected to a vacuum pump (not shown) in orderto control the pressure inside the load lock chamber 3000. When thepressure inside the main chamber 4000 is maintained low, the pressureinside the load lock chamber 3000 may be adjusted to prevent failures ofthe semiconductor substrate inspection equipment due to a pressuredifference between the main chamber 4000 and the load lock chamber 300.

Referring to FIGS. 1 and 2, the main chamber 4000 may include the secondholder 20, a second holder movement track t, a helium ion module 10, thedetector 30, and an optical microscope 4010. The second holder 20 iswhere a substrate transferred by the second robot arm 3010 is placed.The second holder 20 can be used as a wafer stage when a substrate isinspected using an HIM. After being loaded with a substrate by thesecond robot arm 3010, the second holder 20 may move to where the heliumion module 10 is located along the second holder movement track t. Thesecond holder 20 may move in a first direction x and the seconddirection y to adjust the positional relationship between the substrateand the helium ion module 10 and may move in a third direction z toadjust the focus. The second holder 20 may rotate about an optical axisof the helium ion module 10 to align the substrate. In addition, thesecond holder 20 may be tilted with respect to an axis included in thesecond holder 20, so that the substrate can be inspected in a tiltedposition. For example, the second holder 20 may be tilted with respectto an x axis or a y axis, thereby tilting the substrate.

The helium ion module 10 is equipment that irradiates helium ions onto asubstrate placed on the second holder 20. The helium ion module 10 isfixed to the main chamber 4000 since the movement of the helium ionmodule 10 can change set values of the semiconductor substrateinspection equipment. The detector 30 detects particles, e.g., secondaryelectrons, generated from a substrate by helium ions irradiated to thesubstrate. In FIG. 1, the detector 30 is fixed to the periphery of themain chamber 4000. However, the present inventive concepts are notlimited thereto. That is, the detector 30 can be located in an internalspace of the main chamber 4000 and/or can rotate around the secondholder 20. The optical microscope 4010 may be used to optically inspectthe surface of a substrate. The helium ion module 10 and the detector 30will be described in greater detail later with reference to FIGS. 3, 7and 8.

The controller 40 can control the semiconductor substrate inspectionequipment according to various embodiments of the present inventiveconcepts. In FIGS. 1 and 2, the controller 40 is connected to thedetector 30. However, this is for illustrative simplicity only, and thepresent inventive concepts are not limited thereto. For example, thecontroller 40 may convert a signal detected by the detector 30 into animage signal. The controller 40 may control the operation of the heliumion module 10, the movement of the second holder 20 and/or the operationof the load lock chamber 3000. The controller 40 may include acalculator 40 a (see FIG. 3) which can measure a step height of apattern using an image obtained by the detector 30. Specifically, apattern having a step may be formed on a substrate to be inspected. Inthis case, the calculator 40 a of the controller 40 may measure a stepheight of the pattern formed on the substrate using an image obtained bythe detector 30 through the inspection of the substrate. Specificembodiments for measuring a step height of a pattern will be describedin greater detail later with reference to FIGS. 9 and 10.

A process in which substrates to be inspected are moved in thesemiconductor substrate inspection equipment will now be describedbriefly with reference to FIGS. 1 and 2. A plurality of cassettes (notshown) containing substrates to be inspected are fed into the load port1000. The first robot arm 2020 picks up a substrate from a cassette andtransfers the substrate to the first holder 3020 of the load lockchamber 3000. Here, the place where the first holder 3020 is located andthe front-end module 2000 may be made to have the same pressure. Thepressure in the place where the first holder 3020 is located in the loadlock chamber 3000 and the pressure in the place where the second robotarm 3010 is located in the load lock chamber 3000 are adjusted to be thesame. Then, the third gate valve 3000 c is opened. The second robot arm3010 transfers the substrate placed on the first holder 3020 to thesecond holder 20 in the main chamber 4000. Here, the pressure in theplace where the second robot arm 3010 is located and the pressure in themain chamber 4000 are adjusted to be the same. Then, the second gatevalve 3000 b is opened. The substrate placed on the second holder 20 ismoved to under the helium ion module 10 by the second holder movementtrack t. The detector 30 detects particles generated by helium ionsirradiated from the helium ion module 10, and the controller 40connected to the detector 30 displays the detected particles as animage. If a pattern having a step is formed on the substrate, thecalculator 40 a of the controller 40 measures a height of the step anddisplays the measured step height.

Referring to FIGS. 3 through 5, a HIM used in an embodiment of thepresent inventive concepts includes a helium ion module 10 (see FIG. 1),a wafer stage 20, a secondary electron detector 30, and a controller 40.The helium ion module 10 includes a helium gas container 110, a heliumion generator 100, a tube 120, and a cooling device 130. FIG. 3 shows aregion H of FIG. 1.

Semiconductor substrate inspection equipment according to someembodiments of the present inventive concepts includes a gas container110, a helium ion generator 100 located in the helium gas container 110,and a tube 120 located under the gas container 110. The semiconductorsubstrate inspection equipment further includes the wafer stage 20located under the tube 120, a secondary electron detector 30 locatedover the wafer stage 20, a cooling device 130 disposed on the gascontainer 110 and coupled to the helium ion generator 100, and acontroller 40 connected to the secondary electron detector 30. Thesemiconductor substrate inspection equipment further includes a liquidnitrogen dewar 140 and a compressor 150 sequentially connected to thecooling device 130. As known to those having skill in the art, a dewaris a double walled flask of, for example, metal and/or silvered glass,with a vacuum or other substance such as liquid nitrogen, between thewalls, that is used to hold liquids at well below ambient temperature.

Specifically, the helium ion generator 100 converts helium gas 100 ainto helium ions. The helium ion generator 100 is located in the gascontainer 110 that contains the helium gas 100 a. In the drawings, apart of the helium ion generator 100 is located within the gas container110, and the other part of the helium ion generator 100 protrudes upwardfrom the gas container 110. However, the whole of the helium iongenerator 100 can also be located within the gas container 110. Anelectrode (not shown) is installed under the helium ion generator 100 inorder to apply a high voltage to the helium ion generator 100. Since thehelium ion generator 100 is maintained at a low temperature by thecooling device 130, the helium gas 100 a adheres to the helium iongenerator 100. Here, the helium gas 100 a loses electrons to the heliumion generator 100 and is released at high speed toward the wafer stage20 to form helium ions 100 i. Since the helium ions 100 i form a heliumion beam, it will hereinafter be understood that the helium ion beamcontains the helium ions 100 i.

Referring to FIGS. 3 and 5, the helium ion generator 100 is installed inthe gas container 110, and the helium gas 100 a having a pressure higherthan a reference pressure is contained in the gas container 110. A partof the gas container 110 may serve as a path of the helium ion beam 100i generated by the helium ion generator 100.

The gas container 110 may receive the helium gas 100 a from a continuoushelium supply device 170. The continuous helium supply device 170 is adevice that continuously supplies the helium gas 100 a for at leastabout 24 hours. The continuous helium supply device 170 may be, forexample, a utility line of a semiconductor production line. A pluralityof gas bombes can also be connected to form the continuous helium supplydevice 170 which supplies the helium gas 100 a. However, it may beefficient to use the utility line of the semiconductor production lineas the continuous helium supply device 170 in order for the spaceutilization of the semiconductor production line.

Referring to FIG. 5, the gas container 110 may further include a firstpressure gauge 110 p which measures the pressure of the helium gas 100 ain the gas container 110 and a third valve v3. The third valve v3 may belocated between the gas container 110 and the continuous helium supplydevice 170. The first pressure gauge 110 p may be electrically connectedto the third valve v3. However, this is merely an example. That is, eachof the first pressure gauge 110 p and the third valve v3 may beconnected to the controller 40. The first pressure gauge 110 p and thethird valve v3 may operate as follows. When a pressure measured by thefirst pressure gauge 110 p is lower than the reference pressure, thefirst pressure gauge 110 p transmits an electrical signal E.S to thethird valve v3. In response to the electrical signal E.S, the thirdvalve v3 is opened to supply the helium gas 100 a to the gas container110. Conversely, when the pressure measured by the first pressure gauge110 p is higher than the reference pressure, the first pressure gauge110 p transmits an electrical signal E.S to the third valve v3. Inresponse to the electrical signal E.S, the third valve v3 is closed.However, the above operation is merely an example. The third valve v3can also be opened or closed manually by observing the pressure measuredby the first pressure gauge 110 p and/or by using the controller 40.

Referring to FIGS. 3 and 4, the cooling device 130 is placed above thegas container 110 and coupled to the helium ion generator 100 so as tocool the helium ion generator 100. The cooling device 130 may use, forexample, liquid nitrogen. The helium ion generator 100 needs to bemaintained at an extremely low temperature to efficiently generate thehelium ion beam 100 i. To this end, the cooling device 130 can reduce orprevent the temperature of the helium ion generator 100 from increasing,so that the helium ion beam 100 i can be generated in a stable manner.Therefore, it may be desirable for the cooling device 130 tocontinuously supply, e.g., liquid nitrogen to the helium ion generator100 in order to continuously cool the helium ion generator 100.

Referring to FIG. 3, the liquid nitrogen dewar 140, the compressor 150,and a continuous nitrogen supply device 160 are sequentially connectedto the cooling device 130. In addition, a second valve v2 and a firstvalve v1 are respectively connected between the liquid nitrogen dewar140 and the compressor 150 and between the compressor 150 and thecontinuous nitrogen supply device 160. The continuous nitrogen supplydevice 160 is a device that continuously supplies nitrogen gas for atleast about 24 hours. The continuous nitrogen supply device 160 may be,for example, a utility line of a semiconductor production line. Aplurality of gas bombes can also be connected to form the continuousnitrogen supply device 160 which supplies nitrogen gas. However, it maybe efficient to use the utility line of the semiconductor productionline as the continuous nitrogen supply device 160 in order for the spaceutilization of the semiconductor production line.

Referring to FIG. 3, the compressor 150 generates liquid nitrogen usingfirst gaseous nitrogen received from the continuous nitrogen supplydevice 160, e.g., the utility line of the semiconductor production line.The liquid nitrogen generated by the compressor 150 is sent to theliquid nitrogen dewar 140 and stored in the liquid nitrogen dewar 140.The liquid nitrogen dewar 140 which stores the liquid nitrogencontinuously supplies the liquid nitrogen to the cooling device 130. Theliquid nitrogen supplied from the liquid nitrogen dewar 140 isevaporated into second gaseous nitrogen by the cooling device 130 and,at the same time, cools the helium ion generator 100. In other words,nitrogen that cools the helium ion generator 100 is changed to the firstgaseous nitrogen between the compressor 150 and the continuous nitrogensupply device 160, to the liquid nitrogen by the liquid nitrogen dewar140, and then to the second gaseous nitrogen by the cooling device 130.Through this process, the cooling device 130 continuously cools thehelium ion generator 100.

Referring to FIG. 4, the liquid nitrogen dewar 140 may further include asecond pressure gauge 140 p that measures the hydraulic pressure of theliquid nitrogen in the container. The second pressure gauge 140 p may beelectrically connected to the compressor 150 and the first and secondvalves v1 and v2. However, this configuration is merely an example. Thatis, the second pressure gauge 140 p can be connected to the controller40, and each of the compressor 150 and the first and second valves v1and v2 can be connected to the controller 40. The compressor 150, thefirst and second valves v2 and v3, and the second pressure gauge 140 pmay operate as follows. When a pressure measured by the second pressuregauge 140 p is lower than the reference pressure, the second pressuregauge 140 p transmits an electrical signal E.S to the first and secondvalves v1 and v2 and the compressor 150. In response to the electricalsignal E.S, the first valve v1 is opened to supply the first gaseousnitrogen to the compressor 150. Also, in response to the electricalsignal E.S, the second valve v2 is opened to allow the compressed liquidnitrogen to be stored in the liquid nitrogen dewar 140. Conversely, whenthe pressure measured by the second pressure gauge 140 p is higher thanthe reference pressure, the second pressure gauge 140 p transmits anelectrical signal E.S to the first and second valves v1 and v2 and thecompressor 150. In response to the electrical signal E.S, the first andsecond valves v1 and v2 are closed, and the compressor 150 stopsrunning. However, the above operation is merely an example. The firstand second valves v1 and v2 can also be opened or closed manually andthe compressor 150 can also be operated manually by observing thepressure measured by the second pressure gauge 140 p. In addition, thesecond pressure gauge 140 p can operate the first and second valves v2and v3 and the compressor 150 using the controller 40.

Referring to FIG. 3, the tube 120 is disposed under the gas container110, and the helium ion beam 100 i generated by the helium ion generator100 flies in the tube 120. The tube 120 may include a lens 120 a and adeflector 120 b. The lens 120 a may control the size of the helium ionbeam 100 i, and the deflector 120 b may control the direction of thehelium ion beam 100 i.

Referring to FIGS. 2 and 3, the wafer stage 20 is located under the tube120 in the path of the helium ion beam 100 i, and a substrate 200 to beinspected is placed on the wafer stage 20. The wafer stage 20 may be thesecond holder 20 of FIG. 1. The wafer stage 20 may move in first throughthird directions x, y, and z which are different from each other. Thewafer stage 20 may rotate the substrate 200 so that the helium ion beam100 i can reach a location to be measured on the substrate 200. Inaddition, the wafer stage 20 may be tilted so that the substrate 200 canbe measured in a tilted position or that the substrate 200 can level offwhen loaded wrongly. In other words, the substrate 200 can be moved bythe wafer stage 20 with five degrees of freedom. However, this is merelyan example used to describe the embodiment of the present inventiveconcepts, and the present inventive concepts are not limited to thisexample.

Referring to FIG. 3, the secondary electron detector 30 is located abovethe substrate 200 and detects secondary electrons generated from thesubstrate 200. The secondary electron detector 30 may be fixed inposition or rotate around the substrate 200 (see 30 in FIGS. 7 and 8) todetect secondary electrons generated from the substrate 200. Thesecondary electron detector 30 collects and/or detects secondaryelectrons generated from the substrate 200 by the helium ion beam 100 iincident on the substrate 200. The secondary electron detector 30detects the amount of secondary electrons generated from the substrate200 and sends information about the detected amount to the controller40.

Referring to FIG. 3, the controller 40 may include a display 40 b whichdisplays information received from the secondary electron detector 30and a calculator 40 a which calculates a step height of a pattern formedon the substrate 200 using the received information. In someembodiments, the display 40 b displays a signal detected by thesecondary electron detector 30 as an image. The display 40 b displays anenlarged image of the substrate 200 brightly when a large amount ofelectrons are detected by the secondary electron detector 30 and darklywhen a small amount of electrons are detected by the secondary electrondetector 30. The calculator 40 a included in the controller 40 will bedescribed later. Other displays, such as numeric and/or graphic displaysmay be provided.

Semiconductor substrate inspection equipment according to otherembodiments of the present inventive concepts will now be described withreference to FIG. 6. The current embodiment is the same as the previousembodiment except for a gas container 110. Therefore, elementssubstantially identical to those of the previous embodiment areindicated by like reference numerals, and thus their description willnot be repeated or made briefly.

FIG. 6 is a diagram of an HIM used in semiconductor substrate inspectionequipment according to other embodiments of the present inventiveconcepts.

Referring to FIG. 6, a gas container 110 containing helium gas 100 a isdisposed on a tube 120, and a helium ion generator 100 is disposed inthe gas container 110. The gas container 110 does not include a lineconnected to a continuous helium supply device. When the HIM is used,the helium gas 100 a is injected into the gas container 110 through agas inlet (not shown) formed in the gas container 110. When the heliumgas 100 a runs short while the HIM is being used, it can be replenishedthrough the gas inlet. The gas inlet can have any shape. Since the gascontainer 110 is just not connected to the continuous helium supplydevice, a line can be connected to the gas container 110 as in FIG. 3,and a helium gas bombe can be connected to the line. The gas container110 may further include a pressure gauge 110 p. However, the presentinventive concepts are not limited thereto.

Semiconductor substrate inspection equipment according to otherembodiments of the present inventive concepts will now be described withreference to FIGS. 7 and 8. These embodiments are the same as theprevious embodiment described above with reference to FIGS. 3 through 5,except for a secondary electron detector 30. Therefore, elementssubstantially similar to those of the previous embodiment are indicatedby like reference numerals, and thus their description will not berepeated or made briefly.

FIGS. 7 and 8 are diagrams of detectors used in semiconductor substrateinspection equipment according to other embodiments of the presentinventive concepts.

Referring to FIG. 7, a secondary electron detector 30 and an iondetector 32 are placed above a wafer stage 20. When a helium ion beam isincident on a substrate 200 to be inspected, the secondary electrondetector 30 detects secondary electrons 200 e generated from substrate200. Information about the detected secondary electrons 200 e istransmitted to a controller 40 and displayed on a display as an image.In addition, the ion detector 32 detects ions 200 i sputtered from thesubstrate 200. Information about the detected ions 200 i is sent to thecontroller 40 and imaged by the display. The mass of helium ions isseveral thousand times greater than that of electrons. Therefore, alarge amount of ions may be sputtered from the substrate 200, unlikewhen electrons are used to inspect the substrate 200. The sputtered ions200 i are called Rutherford backscattering ions (RBIs), and the iondetector 32 detects the RBIs. The amount of RBIs may vary according tothe material composition (dependent on atomic number Z) of the substrate200. Therefore, the difference between materials existing in thesubstrate 200 can be obtained as image information. The presence of theion detector 32 makes it possible to use the semiconductor substrateinspection equipment to detect defects through a contamination andchemical analysis of the substrate 200.

Referring to FIG. 8, a secondary electron detector 30 is placed above awafer stage 20, and a transmission ion detector 34 is placed under thewafer stage 20. When a helium ion beam is incident on a substrate 200 tobe inspected, the secondary electron detector 30 detects secondaryelectrons 200 e emitted upward from the substrate 200. On the otherhand, the transmission ion detector 34 detects helium ions 100 it thattransmit through the substrate 200. A portion of the substrate 200 uponwhich the helium ion beam is incident should be thin enough to allow thehelium ion beam to transmit therethrough. Thus, the substrate 200 may beprocessed to a thickness small enough to allow the helium ion beam totransmit therethrough. In this case, if information about thetransmitted helium ions 100 it detected by the transmission ion detector34 is sent to a controller 40 and imaged by the display, a diffractiongrating pattern of the substrate 200 is created. From the diffractiongrating pattern, the crystal structure of the substrate 200, the stressstate of the substrate 200, the matching relation of patterns formed onthe substrate 200, and the like can be identified. That is, measurementssimilar to those that can be obtained using a transmission electronmicroscope (TEM) can be obtained using an HIM.

In FIGS. 7 and 8, the ion detector 32 or the transmission ion detector34 is provided in addition to the secondary electron detector 30according to an embodiment of the present inventive concepts. However,this is merely an embodiment. For example, both of the ion detector 32and the transmission ion detector 34 can also be provided in addition tothe secondary electron detector 30. Therefore, two or three detectorscan be installed in the HIM.

FIG. 11 is a flowchart of operations that may be performed to measure astep height of a pattern of a microelectronic substrate using a heliumion microscope according to various embodiments described herein. Asillustrated in FIG. 11, step height measurement may be performed byproviding a microelectronic substrate having a pattern at Block 1110,irradiating helium ions onto the substrate at Block 1120 and measuring astep height of the pattern on the substrate by detecting particlesgenerated from the substrate at Block 1130, in response to the heliumions that are irradiated at Block 1120.

FIG. 12 is a flowchart of operations that may be performed to measurestep height corresponding to Block 1130 of FIG. 11. Referring to FIG.12, at Block 1210 a first slope width of the pattern is measured byanalyzing first electrons detected from the substrate before tilting thesubstrate. At Block 1220, a second slope width of the pattern ismeasured by analyzing second electrons detected from the substrate aftertilting the substrate. Finally, at Block 1230, the step height of thepattern is calculated from the first and second slope widths that aremeasured. Various embodiments of step height measurement of FIG. 11 andof measuring step height of FIG. 12 will now be described.

Semiconductor substrate inspection equipment according to otherembodiments of the present inventive concepts will now be described withreference to FIGS. 9A through 10B. These embodiments are the same as theprevious embodiments described above with reference to FIGS. 3 through5, except for a controller 40. Therefore, elements substantiallyidentical to those of the previous embodiment are indicated by likereference numerals, and thus their description will not be repeated ormade briefly.

FIGS. 9A through 10B are diagrams illustrating a calculation of acontroller 40 used in semiconductor substrate inspection equipmentaccording to other embodiments of the present inventive concepts.

Referring to FIG. 9A, a pattern is cut into a substrate 200 to beinspected. The pattern has a height of h and a width of CD21. Thesubstrate 200 is placed on a wafer stage without being tilted (i.e., atilt angle of about zero). That is, the substrate 200 has no slopewidth. Here, the slope width refers to a width of a sidewall of thepattern when the pattern on the substrate 200 is shown in a plane. Inaddition, the width of the pattern denotes a width of the pattern whenthe pattern on the substrate 200 is shown in a plane. Referring to FIG.3, when the substrate 200 is not tilted, undeflected helium ions 100 iare irradiated to the substrate 200 in a direction perpendicular to thesubstrate 200. That is, the undeflected helium ions 100 i aresubstantially parallel to a normal to the substrate 200.

Referring to FIG. 9B, when the substrate 200 is tilted at an angle of a,the width of the pattern becomes CD22, and the slope width becomes d.Even if the substrate 200 is tilted at an angle of a, the height of thepattern remains at h. The relation between the height h of the pattern,the slope width d, and the tilt angle a of the substrate 200 can bedefined using a trigonometric function as in Equation (1).

h=d/sin(a)  (1).

Referring to FIGS. 9A and 9B, a rectangular pattern having a slope widthof 0, a width of CD21 and a height of h is provided on a substrate 200.After the substrate 200 is tilted, if the slope width is measured usingan HIM, the height h of the pattern can be obtained from the relationdefined by Equation (1).

Calculating a height of a pattern when the pattern having a generalshape is formed on a substrate will now be described with reference toFIGS. 10A and 10B.

Referring to FIG. 10A, a pattern is provided in a substrate 200 to beinspected, corresponding to Block 1110 of FIG. 11. The pattern has aheight of h and a slope width of S1, and a lower part of the pattern hasa width of CD21. In FIG. 10A, the substrate 200 is placed on a waferstage without being tilted.

Referring to FIG. 10B, the substrate 200 is tilted at an angle of a. Inthis case, the width of the lower part of the pattern becomes CD22, andthe slope width becomes S2. Even if the substrate 200 is tilted at anangle of a, the height of the pattern remains at h. The relation betweenthe height h of the pattern, the slope width d, and the tilt angle a ofthe substrate 200 is obtained using a trigonometric function. The slopewidth S2 after the substrate 200 is tilted is the sum of a portion Sresulting from the slope width S1 before the substrate 200 is tilted anda portion d resulting from the height h of the pattern. In addition, acosine component of the slope width S1 before the substrate 200 istilted is S. This can be defined by Equations (2) and (3).

S2=S+d  (2).

S=S1*cos(a)  (3).

The relation between the height h of the pattern and the slope width dresulting from the height h of the pattern still satisfies Equation (1).Therefore, Equations (2) and (3) can be rearranged and substituted forEquation (1) to obtain the relation defined by Equation (4).

h=(S2−S1*cos(a))/sin(a)  (4).

In Equation (4), if zero is substituted for the slope width S1 beforethe substrate 200 is tilted, the same result as that of Equation (1) canbe obtained.

Referring to FIGS. 10A and 10B, a trapezoidal pattern is formed on asubstrate 200 to be inspected. The pattern has a slope width of S1 and aheight of h, and a width of a lower part of the pattern is CD21. Theslope width S1 before the substrate 200 is tilted is measured using anHIM, corresponding to Block 1210 of FIG. 12, and the slope width S2after the substrate 200 is tilted is measured using the HIM,corresponding to Block 1220 of FIG. 12. Then, the height h of thepattern can be obtained from the relation defined by Equation (4),corresponding to Block 1230 of FIG. 12.

Referring to FIGS. 3 and 9A through 10B, a calculator 40 a included inthe controller 40 of the semiconductor substrate inspection equipmentaccording to embodiments of the present inventive concepts can measure astep height of a pattern formed on a substrate 200 to be inspected. Thecalculator 40 a can calculate the step height of the pattern formed onthe substrate 200 based on the relations defined by Equations (1) and(4). In FIGS. 9A through 10B, a case where a height of a pattern formedintentionally is measured is illustrated. However, step heights ofdefects formed on the substrate 200 can also be calculated using thecalculator 40 a.

The gas container 110 and the detectors described above with referenceto FIGS. 6 through 8 can be applied to the semiconductor substrateinspection equipment which includes the calculator 40 a described abovewith reference to FIGS. 9A through 10B.

Hereinafter, a semiconductor substrate inspection method according toembodiments of the present inventive concepts will be described withreference to FIGS. 3 and 9A through 10B.

Referring to FIG. 3, a substrate 200 to be inspected is provided on awafer stage 20. Patterns, such as the pattern shown in FIG. 9A or 10A,are provided on the substrate 200, corresponding to Block 1110 of FIG.11. Helium ions 100 i generated by a helium ion generator 100 of an HIMare irradiated to the substrate 200, corresponding to Block 1120 of FIG.11. Particles (e.g., secondary electrons) generated as the helium ions100 i collide with the substrate 200 are detected by a detector 30. Byanalyzing the detected particles, the shape or step height of thepatterns formed on the substrate 200 is measured, corresponding to Block1130 of FIG. 11. The following description will be based on theassumption that the particles generated from the substrate 200 aresecondary electrons.

First, the secondary electrons generated from the substrate 200 may beanalyzed, and the surface shape of the substrate 200, for example, thepatterns formed on the substrate 200 may be displayed on a display 40 bbased on the analysis of the secondary electrons. To obtain a clearimage based on the surface shape of the substrate 200 displayed on thedisplay 40 b, focal distance, the intensity of helium ions, and the likemay be adjusted. In addition, the wafer stage 20 may be rotated ortilted between the irradiating of the helium ions 100 i to the substrate200 and the measuring of the step height of the patterns formed on thesubstrate 200. The patterns formed on the substrate 200 may be patternsarranged in an arbitrary direction. For example, to measure the shape orstep height of the patterns arranged in an arbitrary direction, thesubstrate 200 may need to be rotated. Specifically, a direction in whichthe substrate 200 is inspected may be different from a direction of thepatterns formed on the substrate 200. In this case, for efficientpattern inspection, the substrate 200 placed on the wafer stage 20 maybe rotated to align the inspection direction with the direction of thepatterns. That is, between the irradiating of the helium ions 100 i tothe substrate 200 and the measuring of the step height of the patternsformed on the substrate 200, the direction of the patterns may beadjusted by rotating the substrate 200 in order to align the inspectiondirection of the substrate 200 with the direction of the patterns formedon the substrate 200.

Referring to FIG. 3, the undeflected helium ions 100 i may beperpendicularly incident on the wafer stage 20 without the substrate200. In this state, if the substrate 200 is placed on the wafer stage20, the undeflected helium ions 100 i may be perpendicularly incident onthe substrate 200. However, particles may exist between the wafer stage20 and the substrate 200, or a thickness of an adhesive member may notbe uniform. In this case, the undeflected helium ions 100 i may not beperpendicularly incident on the substrate 200. Then, errors may occurwhen the step height of the patterns formed on the substrate 200 ismeasured. To reduce or prevent such errors, the substrate 200 may needto be put in a non-tilted position. Therefore, the slope of thesubstrate 200 placed on the wafer stage 20 may be adjusted before thestep height of the patterns formed on the substrate 200 is measured, sothat the undeflected helium ions 100 i are perpendicularly irradiated tothe substrate 200.

Referring to FIGS. 3, 10A and 10B, the detector 30 detects firstsecondary electrons generated from the substrate 200 in a non-tiltedposition, that is, before the substrate 200 is tilted. The controller 40connected to the detector 30 measures a first slope width S1 of thepatterns formed on the substrate 200 by analyzing the first secondaryelectrons, corresponding to Block 1210 of FIG. 12. Then, the substrate200 is tilted at an angle of a. The detector 30 detects second secondaryelectrons generated from the tilted substrate 200. The controller 40measures a second slope width S2 of the patterns formed on the substrate200 by analyzing the second secondary electrons, corresponding to Block1220 of FIG. 12. Using the measured first slope width S1 and themeasured second slope width S2, the controller 40 calculates the stepheight of the patterns formed on the substrate 200, corresponding toBlock 1230 of FIG. 12. The controller 40 can calculate the step heightof the patterns using Equation (4) described above.

Accordingly, microelectronic substrates may be inspected according tovarious embodiments described herein by measuring a step height of apattern on a microelectronic substrate using an HIM. The measuring maytake place by measuring a slope width of the pattern at two differenttilt angles of the microelectronic substrate relative to the helium ionmicroscope. One of the two different tilt angles may be about zerodegrees. The helium ion microscope may be operated continuously duringthe measuring of the slope width of the pattern at the two differenttilt angles of the microelectronic substrate relative to the helium ionmicroscope.

The step height of a pattern can be measured more accurately using anHIM than using a conventional SEM for at least the following reasons.

Theoretically, a maximum spatial resolution of the HIM is approximately0.25 nm. Therefore, when the HIM is used, a pattern at a distance ofmore than 0.25 nm can be identified using a measured image. Since awidth of a fine pattern can also be identified using the HIM, accuratemeasurement is possible. In addition, a relatively greater amount ofsecondary electrons are generated from the surface of a substrate whenthe HIM is used than when the SEM is used. Therefore, a high-contrast,sharp image can be obtained using the HIM. Also, since different ionsare generated according to respective elements, an image with sharpcontrast can be obtained. Further, compared with the SEM, the HIM has alarge depth of field (DOF) and high resolution due to its very smallhalf conical angle and small volume of interaction with a substrate tobe inspected. The DOF is a value indicating the distance in front of andbehind a subject which appears to be in focus. Since the HIM has a largeDOF, it can obtain a sharp image as sharp as a planar image of even apattern with a large step height. Therefore, when the HIM is used,blurry images which are out of focus can be reduced, and a width of apattern can be measured using a sharp image. Using precise measuredvalues, the step height of a pattern can be calculated precisely byEquation (1) or (4).

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, the present specification, including the drawings, shall beconstrued to constitute a complete written description of allcombinations and subcombinations of the embodiments described herein,and of the manner and process of making and using them, and shallsupport claims to any such combination or subcombination.

While the present inventive concepts have been particularly shown anddescribed with reference to various embodiments thereof, it will beunderstood by those of ordinary skill in the art that various changes inform and details may be made therein without departing from the spiritand scope of the present inventive concepts as defined by the followingclaims. It is therefore desired that the present embodiments beconsidered in all respects as illustrative and not restrictive,reference being made to the appended claims rather than the foregoingdescription to indicate the scope of the invention.

1. Microelectronic substrate inspection equipment comprising: a heliumgas container containing helium gas; a helium ion generator that isconfigured to convert the helium gas into helium ions; a wafer stagewhich is disposed in a path of the helium ions and is configured forplacing a microelectronic substrate to be inspected thereon; a secondaryelectron detector which is disposed adjacent the wafer stage and isconfigured to detect electrons generated from the substrate; acompressor which is configured to receive first gaseous nitrogen from acontinuous nitrogen supply device and to compress the received firstgaseous nitrogen into liquid nitrogen; a liquid nitrogen dewar which isconnected to the compressor and is configured to store the liquidnitrogen; and a cooling device which is coupled to the helium iongenerator and configured to cool the helium ion generator by vaporizingthe liquid nitrogen received from the liquid nitrogen dewar into secondgaseous nitrogen.
 2. The inspection equipment of claim 1: wherein thehelium ion generator is disposed in the helium gas container; whereinthe wafer stage is disposed under the helium gas container; wherein thesecondary electron detector is disposed above the wafer stage; andwherein the cooling device is disposed on the helium gas container. 3.The inspection equipment of claim 1, wherein when pressure of the liquidnitrogen dewar is a reference pressure or less, the compressorcompresses the first gaseous nitrogen received from the continuousnitrogen supply device into the liquid nitrogen and stores the liquidnitrogen in the liquid nitrogen dewar.
 4. The inspection equipment ofclaim 1, wherein the helium gas container receives helium gas from acontinuous helium supply device.
 5. The inspection equipment of claim 3,further comprising a valve disposed between the helium gas container andthe helium supply device and a pressure gauge connected to the heliumgas container.
 6. The inspection equipment of claim 5, wherein the valveis opened or closed in response to a signal received from the pressuregauge.
 7. The inspection equipment of claim 1, further comprising an iondetector which is disposed above the wafer stage and detects ionssputtered from the substrate.
 8. The inspection equipment of claim 1,further comprising a transmission ion detector which is disposed underthe wafer stage and detects the helium ions which transmit through thesubstrate.
 9. The inspection equipment of claim 1, wherein the waferstage is configured to move the substrate in three different directions,rotate the substrate, and/or tilt the substrate.
 10. The inspectionequipment of claim 1, wherein the secondary electron detector isconfigured to rotate around the wafer stage.
 11. The inspectionequipment of claim 1, further comprising a display which displays asignal received from the secondary electron detector as an image.12.-20. (canceled)